Android四大组件应用系列——使用ContentProvider实现跨进程通讯

一、问题描述

　　如何在Android中实现不同应用之间的通讯（既跨进程进行调用）？Android提供了多种实现方式，使我们可以实现跨进程访问Activity、通过ContentProvider跨进程访问其他应用的数据、通过Broadcast可以向android系统中所有应用程序发送广播、使用AIDL实现跨进程的Service。下面我们就使用ContentProvider实现跨进程访问数据，并可对数据进行增、删、改、查

二、应用实现

　　使用ContentProvider实现数据共享，主要是共享应用的Sqlite数据库，再一个应用中（本例的shareinfo）提供数据源（Sqlite数据库）并创建ContentProvider组件， ContentProvider组件主要对外（其他应用）提供访问数据的接口（Uri信息），其他应用（本例的other）通过这个接口（Uri信息）实现跨进程的方法调用

　　如图所示：

　　本例涉及两个应用shareinfo和other

三、shareinfo应用的核心

　　作为数据的提供者首先是开发对外可访问的数据库（Sqlite）

　　涉及两个组件DbOpenHelper和SQLiteHelper

　　代码如下：

public class DbOpenHelper extends SQLiteOpenHelper {
    public DbOpenHelper(Context context) {
        super(context, "jereh.db", null, 4);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table person(personid integer primary key " +
                " autoincrement,name varchar(20),phone varchar(12) null)");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL("drop table person");
        onCreate(db);
    }
}

public class SQLiteHelper {

    private Context context;
    private DbOpenHelper  helper = null;
    public SQLiteHelper(Context context){
        helper = new DbOpenHelper(context);
    }

    public void save(Person person){//增
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("insert into person(name,phone) values(?,?)",new Object[]{person.getName(),person.getPhone()});
        db.close();
    }
    public void delete(int personid){//删
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("delete from person where personid=?", new Integer[]{personid});
        db.close();
    }
    public void update(Person person){//改
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("update person set name=?,phone=? where personid=?", new Object[]{person.getName(),person.getPhone(),person.getPersonid()});
        db.close();
    }
    public Person find(int personid){//查
        SQLiteDatabase db = helper.getReadableDatabase();
        //Cursor cursor = db.rawQuery("select * from person where personid=?", new String[]{personid+""});
        Cursor cursor=db.rawQuery("select * from person",null);
        if(cursor.moveToFirst()){
            int id = cursor.getInt(cursor.getColumnIndex("personid"));
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String phone = cursor.getString(cursor.getColumnIndex("phone"));
            return new Person(personid, name, phone);
        }
        cursor.close();
        return null;
    }

}

然后编写ContentProvider组件代码如下：

package com.jereh;

public class PersonProvider extends ContentProvider {

    private DbOpenHelper openHelper;
    private static final UriMatcher MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
    private static final int PERSONS = 1;
    private static final int PERSON = 2;
    static{
        MATCHER.addURI("com.jereh.providers.personprovider", "person", PERSONS);
        //* 根据pesonid来删除记录
        MATCHER.addURI("com.jereh.providers.personprovider", "person/#", PERSON);
    }
    @Override
    public boolean onCreate() {
        openHelper = new DbOpenHelper(this.getContext());
        return false;
    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        SQLiteDatabase sqLiteDatabase = openHelper.getReadableDatabase();
        switch (MATCHER.match(uri)) {
        case 1:
            return sqLiteDatabase.query("person", projection, selection, selectionArgs, null, null, sortOrder);
        case 2:
            long rowid = ContentUris.parseId(uri);
            String where = "personid="+rowid;
            if(selection != null && "".equals(selection.trim())){
                where = selection+"and"+where;
            }
            return sqLiteDatabase.query("person", projection, where, selectionArgs, null, null, sortOrder);
        }
        return null;
    }

    @Override
    public String getType(Uri uri) {
        switch (MATCHER.match(uri)) {
        case 1:
            return "vnd.android.cursor.dir/person";
        case 2:
            return "vnd.android.cursor.item/person";
        }
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
        switch (MATCHER.match(uri)) {
        case 1:
            long rowid = sqLiteDatabase.insert("person", "name", values);
            return ContentUris.withAppendedId(uri, rowid);

        default:
            break;
        }
        return null;
    }

    //* 删除特定personid行的记录
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
        switch (MATCHER.match(uri)) {
        case 1:
            return sqLiteDatabase.delete("person", selection, selectionArgs);
        case 2:
            long rowid = ContentUris.parseId(uri);
            String where = "personid="+rowid;
            if(selection != null && "".equals(selection.trim())){
                where = selection+"and"+where;
            }
            return sqLiteDatabase.delete("person", where, selectionArgs);
        }
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        SQLiteDatabase sqLiteDatabase = openHelper.getWritableDatabase();
        switch (MATCHER.match(uri)) {
        case 1:
            return sqLiteDatabase.update("person", values, selection, selectionArgs);
        case 2:
            long rowid = ContentUris.parseId(uri);
            String where = "personid="+rowid;
            if(selection != null && "".equals(selection.trim())){
                where = selection+"and"+where;
            }
            return sqLiteDatabase.update("person", values, where, selectionArgs);
        }
        return 0;
    }
}

在AndroidManifest.xml中注册provider

  <provider android:name="com.jereh.PersonProvider"
            android:authorities="com.jereh.providers.personprovider">

shareinfo应用编写完成

四、编写other应用

　　接下来编写other应用，在这个应用中访问shareinfo中数据，我们使用Android JUnit进行测试，开发单元测试组件如下：

public class AccessProvider extends AndroidTestCase {
    public void testInsert(){
        Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person");
        ContentResolver resolver = this.getContext().getContentResolver();
        ContentValues values = new ContentValues();
        values.put("name", "xiaoli");
        values.put("phone", "333333");
        resolver.insert(uri, values);
    }

    public void testDelete(){
        Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person/2");
        ContentResolver resolver = this.getContext().getContentResolver();
        resolver.delete(uri, null, null);
    }
    public void testUpdate(){
        Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person/3");
        ContentResolver resolver = this.getContext().getContentResolver();
        ContentValues values = new ContentValues();
        values.put("name", "ljb");
        values.put("phone", "00000000");
        resolver.update(uri, values, null, null);
    }

    public void testQuery(){
        Uri uri = Uri.parse("content://com.jereh.providers.personprovider/person");
        ContentResolver resolver = this.getContext().getContentResolver();
        Cursor cursor = resolver.query(uri, new String[]{"name","phone"}, null, null, null);
        while(cursor.moveToNext()){
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String phone = cursor.getString(cursor.getColumnIndex("phone"));
            System.out.println("name="+name+" "+"phone="+phone);
        }
    }
}

执行单元测试，测试结果如图所示：

　　所有方法均通过了测试，实现了在一个应用（other）中访问另一个应用（shareinfo）中的数据

　　AndroidManifest.xml配置：

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.jereh.other.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
              <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <uses-library android:name="android.test.runner" />
    </application>
    <instrumentation
    android:name="android.test.InstrumentationTestRunner"
    android:targetPackage="com.jereh" android:label="My Test">
    </instrumentation>

作者：杰瑞教育
出处：http://www.cnblogs.com/jerehedu/ 
版权声明：本文版权归烟台杰瑞教育科技有限公司和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

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